1. Field of the Invention
The present invention relates to a development device for developing a latent image by causing the adherence of a toner, which is being made to hop between the electrodes on the surface of a toner bearing member that comprises a plurality of electrodes, to the latent image on a latent image bearing member of an image forming apparatus. Further, the present invention relates to an image forming apparatus that uses this development device.
2. Description of the Related Art
Instead of a conventional development device that uses a toner, which has been made to adhere to the surface of a development roller or the like, in development, a development device that uses a toner, which is caused to hop on the surface of a toner bearing member like the disclosures in Japanese Patent Laid-Open No. 2002-341656 (referred to herein as Prior Art 1) and Japanese Patent Laid-Open No. 2007-133376 (referred to herein as Prior Art 2) in development, is known.
In these prior art development devices, hopping causes the toner, which is not demonstrating adsorption force relative to the surface of the toner bearing member, to transfer to the latent image bearing member from the surface of the toner bearing member. Consequently, in a conventional one-component development system or two-component development system, it is possible to realize more low-potential development than expected. For example, it is also possible to cause toner to selectively adhere to an electrostatic latent image for which the potential difference with the surrounding non-image part is a mere several tens of volts [V].
However, in these development devices, if any of the electrodes are partially damaged, it is highly likely that toner hopping performance on the toner bearing member will deteriorate enough to impede development. Specifically, the size in the lateral direction (width direction) of a strip-shaped electrode, which is formed on a toner transporting substrate and toner bearing roller serving as the toner bearing member, is extremely narrow at around several tens of micrometers (μm). The reason for making the electrode narrow like this is so that, no matter what location in the width direction of the electrode that the toner resides on the electrode, the toner can be made to reliably hop from this location toward the adjacent electrode. The surface of the toner bearing member is covered with a surface layer comprising an insulating material for the purpose of avoiding the injection of a charge into the toner from the electrode, but variations in precision at the time of fabrication and partial scraping can result in extremely thin spots in the surface layer. This can cause a sudden discharge of electricity between electrodes via these thin spots, partially damaging the electrodes. Further, there are also cases in which the electrodes are partially damaged by workers accidentally bumping their tools against the electrodes when carrying out maintenance. When these partially damaged areas electrically disconnect the narrow electrodes, electric current no longer flows to locations in the current path downstream from these damaged spots. Then, toner hopping performance is lost in these downstream locations.